Antistatic device



Aug. 15, 1961 R. M, WILSON ANTISTATIC DEVICE Filed Jan. 9, 1957 n l I ll RichardMWilson INVENTOR. Q BY N.

ATTORNEYS United States Patent Oiice 2,996,646 Patented Aug. 15, 19612,996,646 ANTISTATIC DEVICE Richard M. Wilson, Rochester, N.Y., assignorto Eastman Kodak Company, Rochester, N.Y., a corporation of New JerseyFiled Jan. 9, 1957, Ser. No. 633,224 7 Claims. (Cl. 3'17-2) Thisinvention relates to antistatic apparatus. More particularly it relatesto a special roll construction which may be used in conjunction with thehandling of photographic tilm under conditions where static electricitymay be generated.

Itis well-known in industry that the handling of webs or `otherattenuated material such as the passage of film over rollers or insliding contact lwith other apparatus parts, particularly underconditions of high speed, considerable static electricity may begenerated with the attendant problems and diiiiculties. While theproblem of the generation of static electricity is encountered in anumber of fields, such as in the textile industry, the paper makingindustry and the like, the problem' may be especially troublesome in thephotographic field. That is, for example, in the manufacture ofphotographic film where the film carries a light-sensitive layer, it isapparent that static discharge, if it occurs in the vicinity of thelight-sensitive coating, may cause damage thereto. Of course, inindustry at large, as for example in industries Where webs are coatedwith coatings containing volatile solvents, the discharge of staticelectricity can present the hazard of igniting solvent vapors.

Accordingly, a considerable amount of work has been done in the fieldfor reducing or minimizing the generation of static. Much of this workappears to involve applying so-called antistatic surface coatings on thematerials being processed. That is, a considerable number of chemicalcompositions have been suggested which may be applied as treating agentsor dressing to textiles, paper and the like for minimizing the formationof static. For example, in the photographic industry there is frequentlyapplied to photographic film a separate layer known as an antistaticlayer. There are, of course, many other procedures which have beensuggested, such as wetting the surfaces and the like.

While, as indicated, considerable work has been carried out which can begenerically referred to as surface treatment of the material beingprocessed, there has been some work done `on apparatus construction anddesign for minimizing the static problem. For example, a number ofapparatus constructions .have been provided which contain conductingdevices adapted to be positioned in the vicinity of the moving webmaterial, which conducting devices tend to drain off the static charges.Although the prior apparatus :and processes have aided in combating thestatic problem, as far as I am aware there is no complete procedure orapparatus that has been developed which entirely combats the problem.

It is apparent, therefore, that the development of means which furtherassist in reducing or minimizing static represents a highly desirableresult. After extended investigation I have found apparatus constructionwhich has substantial utility in the vhandling of web materials underconditions where static electricity may be generated. My apparatus isparticularly useful in that it can be incorporated into existingequipment with a minimum of reconstruction and may be readily used inthe conveying or other handling of web products which continue to carrythe customary coatings or layers including antistatic coatings.

This invention has for one object to provide a construction feature ondevices, which devices may be used in the conveying or handling of webmaterial under conditions where static may be generated. A particularobject is to provide devices which are useful in the photographicindustry under conditions of contacting the photographic product whereinstatic electricity may be generated. A still further object is toprovide devices of the ltype indicated wherein an antistatic component,rather than being present as a surface treatment, is internallyincorporated into said devices or a part of said devices. A stillfurther object is to provide a composite roll of a constructionparticularly adapted for the handling and conveying of photographic filmunder conditions where static electricity may be generated but whereinsaid roll construction minimizes or combats said static. A still furtherobject is to provide devices of the type indicated Which lend themselvesto ready and economical incorporation in existing equipment as asubstitute or replacement for parts now in use which tend to produce arather high quantity of static electricity.

I have found that certain parts of the equipment used in photographicwork for handling film under conditions where static is generated may beconstructed of plastic materials in which certain chemical agents, aswill be described in detail hereinafter, are incorporated internally insaid plastic. This internal incorporation in the plastic is in contrastto the surface treatment which has heretofore been employed. I havefound that in so making these parts which contact the web material ofplastic having internally incorporated chemical agent, that thegeneration of static is substantially minimized. I have further found inthe construction of my invention that if the surface becomes dirty, suchsurface may be washed, shaved off or otherwise restored and theantistatic properties are still present. This is of considerableadvantage over prior art procedures where the mere surface treatment wasrelatively temporary and incapable of restoration.

While my invention may be applied in the manufacture of variousphotographic equipment such as dark slides for sheet film holders,camera parts, conveyor parts in continuous processing equipment orconveyor parts for the handling of powders and other nely dividedmaterials and the like, I will illustrate my invention with particularreference to a roll construction such as may be used in variousphotographic equipment wherein photographic rdm is conveyed atrelatively high speeds.

For assistance in understanding of the present invention reference ismade to the attached drawing forming a part of the present application.In the attached drawing the single figure shows a cross-section of aroll in accordance with the present invention.

In the attached drawings 2 and 3 are metal end plugs for forming the endportion of my roll. Such end plugs are provided with enlarged boredcenter sections 4 and 6 through which suitable axle members 7 and 8 maybe extended. These axle means upon which the rolls may rotate would becarried in conventional bearing members 9 and 11. `It is suicient topoint out that the various parts just referred to which govern therotatability of the roll would be constructed in sufficiently carefulpractice so that the roll would be run true.

The end plugs 2 and 3 are provided at -12 and 13 with diange or skirtportions which are adapted to receive the outer cylinder `or tube member14.

This tube member, as well as the end members, may be constructed fromaluminum. This outer cylinder is fastened to the end plugs as at 16 and17 by welding or in some other suitable manner.

Over this cylinder or tube member 14 in particular, and also preferablyover the surface of end plugs 2 :and 3, there is positioned the plasticmember of the present invention, designated 18.

In the broader aspects of this invention this plastic material may becomprised of various types of plastic.

However, it is preferred to employ a plastic essentially comprised of Iaphenol formaldehyde condensation product impregnated in a fibrousmaterial. In any event, the plastic has thoroughly incorporated into it(rather than a surface treatment) certain chemical agents which will bedescribed in detail hereinafter. This plastic having the agentinternally inconporated therein, is inmly alixed to the outer surface ofthe roll. In this instance that the laminated `phenol formaldehydeproduct is employed in accordance with the preferred embodiment, suchlaminated plastic may be wound onto cylinder 14 then by heating,pressing and the like treatment, caused to attach firmly thereto.

In further detail, laminated phenol formaldehyde plastic sheet can bewound onto tube 14 while it is rotating on a mandrel. After a sufficientthickness, which may vary from 1/10 up to 1A", has been wound onto themetal cylinder under tension, the winding may be caused to set up withheat, leaving a surface which is then finished by machining to thedesired degree of smoothness. The aforementioned Winding under tensionis usually under sufficiently high tension as to impart pressure on thelayer.

The roll of the present invention having the external plastic surface inwhich plastic surface certain chemical agents are internallyincorporated, will operate in contact with moving webs without thegeneration of Vas much static as is experienced when, for example,metals rolls are employed. However, with my novel construction justdescribed wherein there is a metal center such as the aluminum partsjust described, such metal parts apparently may act as a conductor todrain oif static electricity through axle 7 and 8 and into the frameworkof the structure supporting the rolls.

Further details concerning plastic composition, the internallyyincorporated chemical agent and other related data will be apparentfrom the following:

There are several plastic compositions in which the antistatic agents ofthe presentv invention may be incorporated for making the outer surface18. However, I have found that the readily available commercial phenolformaldehyde condensation products comprise very useful plastic for thepresent invention. These plastic materials which are usuallythermosetting may be made by the condensation of a phenol with analdehyde by reacting these ingredients together for a period of time inthe presence of either acid or alkaline catalysts. Usually alkalinecatalysts such as sodium hydroxide, the various amines and the like maybe used. However, the reaction of the phenol and the aldehyde to producethe resinous condensation product may also be carried out in thepresence of certain acids. Also, while I refer to phenol, suitableplastics may also be derived from the reaction product of cresol,xylenols and the like phenolic homologues. Since various methods ofmanufacturing such phenol formaldehyde condensation products are knownin the art, and since the exact condensation product is not a limitationon the present invention, further description on this aspect does notappear to be required. It appears adequate .to indicate that a suitableplastic material is manufactured or obtained.

Then this plastic material has thoroughly incorporated therewith acontent of chemical agent which will act as an antistatic. One suitableprocedure for incorporating the agent into the plastic comprisesdissolving the plastic in a solvent and then adding a solution of theagent to the solution of .the plastic with mixing. In the instance ofphenol formaldehyde plastics various common solvents may be employedsuch as, for example, ethyl alcohol. The solvent solution of the plasticis frequently referred to as a varnish. Then, as just pointed out, tothe varnish is added a content of the Iantistatic agent or agents whichit is desired to thoroughly incorporated Within the plastic.

The agent which I prefer to incorporate in the plastic is a sodium saltof the disulfonic acid formed by condensing two groups of naphthalenesulfonic acid with formaldehyde. This sodium salt of the disulfonic acidproduct just mentioned may be dissolved in water and the aqueoussolution added to the varnish and thoroughly mixed therewith. Furtherdetails concerning the prepara* tion of this particular chemicaladditive may be found in British Patent 7,137 of 1913.

While the chemical agent just mentioned is the preferred additive, thereare other chemical agents which may be employed. For example, in acomparable manner chemicals `such as: alkylated aryl polyether alcoholssuch as polyethylene oxide derivative of tertiary octyl phenoxy ethanol(Triton X100, mfg. by Rohm & Haas Co.) or Stearyl, dimethyl benzylammonium chloride (Triton X400, mfg. by Rohm & Haas Co.) can beincorporated in the plastic.

In accordance with my preferred embodiment, the above-describedsolutions lof the phenolic polymer containing the antistatic agentthoroughly mixed therewith would be employed lto impregnate a brousmaterial such as paper or a fabric. In the impregnating process a rollof the web material, such as cotton fabric, on a mandrel is unwound overa guide means through the bath containing the plastic having theantistatic therein. From this impregnating bath the fabric is Withdrawnin contact with a scraper or other means for removing excess plasticfrom the fabric. The fabric which has been impregnated with the plasticcontaining the antistatic agent of the present invention, is then drawnthrough a long drying chamber heated in some suitable manner such aswith hot air in order to remove most of the alcohol solvent abovementioned. This solvent, of course, may be collected in a recovery plantand reused.

In many instances it is preferred that a small amount of `solvent remainin the impregnated fabric since this prevents the plastic from becominginflexible, thereby rendering further fabrication more diicult.

The impregnated material thus obtained in sheet form may then be woundunder tension around the aluminum cylinder 14 in as many layers as isdesired to produce an outer plastic `coating of from lAO" up to 1A" ormore in thickness. The roll thus covered with the plastic may then besubjected to further treatment under heat and pressure for eliminatingresidual solvent, as well as causing the plastic to harden, therebyproducing a roll which may be machined to a smooth finish.

In most instances where my roll is to be brought in contact withphotographic film, I prefer to roughen the plastic surface somewhat byslightly 4abrading the plastic surface of the rol-l with an abrasivepaper known as Trimite paper of a size varying from 1 to 400. Thisroughening of the surface of the roll is usually insuflcient that theroughness is visible to the eye. However, the roughness of the surface,of course, could be observed upon microscopic examination with a glassof low magnification. A further understanding of my invention will beobtained from consideration of the following examples which are setforth to illustrate the preferred embodiment.

Example I In accordance with this example the plastic solution which wasprepared comprised about 450 lbs. of a phenol formaldehyde varnish. Thesource of the phenol formaldehyde condensation product was a commercialmaterial known as Bakelite. To this varnish was added approximately 25lbs. of the above-mentioned sodium salt of a disulfonic acid formed bycondensing two groups of naphthalene sulfonic acid with formaldehyde.This chemical compound was dissolved in about 45 lbs. of water and theaqueous ysolution was thoroughly mixed into the varnish so that thechemical agent was well distributed through the plastic.

This plastic-additive liquid was then used to impregnate cotton duck ina manner as described above so that the cotton duck contained a contentof plastic to the extent of approximately 45-55%. The cotton duckcontaining this plastic was then subjected to a temperature ofapproximately 300 F. for a short period of time to further polymerizethe materials and harden the product.

The sheet thus obtained was then tightly wound onto an aluminum cylinderas already described, to a thickness of 1/s" in order to form theplastic roller in accordance with the present invention. The surface ofthe resultant roller was roughened slightly with abrasive paper.

Example II In accordance with this example a varnish solution containingthe same additive as set forth in the preceding example was made up.However, in this example the liquid was employed to impregnate paper.The paper, after impregnation, was subjected to a brief heating at above175 F. to obtain further polymerization. The impregnated paper wasapplied to an aluminum cylinder for forming a plastic exterior on theroll as in the preceding example.

The rolls produced in accordance with the above examples were rst testedby vigorous rubbing. No substantial static charge developed on the rollsof the present invention. On the other hand, comparable vigorous rubbingwas performed on stainless steel rolls which had customr arily beenused, and showed the presence of a rather substantial static charge.

'Ihen the rolls in accordance with the present invention were tested incontact with photographic film and a comparison made against stainlesssteel rolls which were used under substantially comparable conditions.The method used is substantially as described in H. W. Cleveland, I. S.M. P. T. E. 55, 37-44, July 1950.

In certain of these tests the film speed was 60 ft./min., film tension(35 mm. strip) 650 grams, angle of wrap film makes with test roller 60degrees, relative humidity 50 percent, and room temperature 75 F.

The summary of data below arrived at from these various tests indicatethe following:

When photographic films have an electrostatic charge level sufficientlyhigh as to cause damage to photo-sensitive layers, it has been foundthat rollers made according to my invention will reduce theelectrostatic charge on the film from 20% to 90% whereas a reduction offrom only to 45% can be realized with stainless steel rollers. In eachcase the lower percentages are found in measurements taken when anon-conducting surface contacts the rollers while the higher percentagesare found when the film surfaces contacting the rollers are conductingin nature.

Furthermore, when a photographic film which has no electrostatic chargeis passed over several rollers in succession, it will tend to electrifyat each roller passage until an equilibrium potential is reached. It hasbeen found when using the rollers described in my invention, theequilibrium level will be only about 5 to 50% of that found in stainlesssteel rollers. The lower percentage is found with films having aconducting surface, while the higher percentage is found with filmshaving a non-conducting surface.

The rolls of the present invention can be readily substituted forconventional metal rolls in photographic processing machines and will,from the mechanical standpoint, handle the film with equal facility butwith less static problems as just indicated.

While in the above examples I have shown my roll made from a plasticcontaining a fabric type of material, and generally prefer that theplastic contain some bonding media, my invention is not limited to thisexact construction. For example, in place of the cotton fabric describedabove, fiber glass and other similar materials may be used for the basewhich is impregnated. While, as indicated, phenol formaldehydecondensation products are preferred because of their favorableelectrical and mechanical properties, in the broader aspects of thepresent invention the use of other suitable plastics is contemplated, aswell as other methods of applying the plastic to the parts to which itis desired to give enhanced antistatic properties. For example,cellulose ester molding pellets may have thoroughly incorporatedtherewith the same additives as described in detail above. This moldingmaterial then may be melt extruded around the rolls in a mannergenerally comparable to the extrusion of insulation around wires.Likewise, while I have illustrated my invention with particularreference to rolls, the plastic of the present invention may be appliedto other parts of photographic equipment where the parts are in contactwith the moving film, and thereby reduce static generation. For example,on dark slides for sheet film holders the slide may be manufactured ofplastic impregnated with the antistatic agent in accordance with thepresent invention.

The percentage of the antistatic agent may be varied from about 5% basedon the weight of the plastic to as high an amount as is reasonablycompatible without materially reducing the strength of the plastic.However, usually not more than about 20% will be required.

Other modifications and uses which may be made are of the followingtype:

For example, various other types of rollers may be manufactured in asimilar manner for use in equipment employed for processing photographicfilm. The principles of the present invention may be used in processeswhere dirt accumulation is incurred by the presence of an electrostaticcharge to minimize such accumulation; other uses may occur to thoseskilled in the art.

It is believed apparent from the foregoing description that improvedapparatus parts have been provided, which parts have particular value inutilization under conditions where static may be generated but withconsiderably lessened and reduced static formation.

I claim:

l. A roll means particularly adapted for use in handling light-sensitivephotographic film products under conditions where contact with the rollmay cause static electricity generation, said roll comprising aluminumend cores provided with means `for receiving axle members, said endcores carrying skirt portions for receiving an aluminum cylinder memberfor forming the roll structure, a layer of laminated phenol fomaldehydecondensation plastic impregnated web encircling at least a major part ofsaid aluminum cylinder, said plastic having a content of at least 5% ofa sodium salt of an acid formed by condensing two groups of naphthalenesulfonic acid with formaldehyde thoroughly incorporated throughout saidplastic, the external surface of said roll structure being slightlyroughened, said roll exhibiting improved antistatic properties.

2. A process of restoring the antistatic properties of a roll having astructure in claim l which comprises removing a small portion of theplastic surface of said roll.

3. A process in accordance with claim 2 wherein the restoration isaccomplished by soaking and washing the surface.

4. The process in accordance with claim 2 wherein the restoration isaccomplished by mechanically scraping a thin layer from the surface.

5. An apparatus part particularly useful for contacting photographicfilm products under conditions where static electricity may begenerated, said part being comprised of a metal inner portion and theouter portion which contacts the film being comprised of a relativelyhard, machinable plastic section between V10 and 1A" thick, said plastichaving incorporated substantially throughout the plastic a content ofthe sodium salt of disulfonic acid formed by condensing two groups ofnaphthalene sulfonic acid with formaldehyde.

6. A roll for use under conditions where static may be generatedcomprising a metal inner member, said metal inner member carrying anouter layer of plastic over substantially the entire metal member, saidplastic being essentially comprised of a laminated phenol formaldehydecondensation product which contains 5 to 50% of a sulfonic acidderivative antistatic agentv thoroughly distributed throughout saidplastic.

7. 'Apparatus parts for use in the photographic industry Where saidparts contact photographic film under conditions where static may begenerated, Said part being composed principally of a relatively hardplastic which may be machined and which contains distributed throughoutthe plastic 5-50% of a sulfonie derivative antistatic agent whereby saidpart exhibits improved antistatic properties.

References Cited in the le of this patent UNITED STATES PATENTS Hazell Jan. 22, 1935 Cutler Aug. 20, 1935 Little Dec. 23, 1941 Kennedy Nov. 17,1942 Harkins July 11, 1944 Holst Apr. 3, 1945 Rockoif Mar. 9, 1948Luaces Apr. 12, 1949 Famulener Feb. 5, 1952 Garrett Nov. 18, 1958

